<button class="inbox-btn">
  <svg viewBox="0 0 512 512" height="16" xmlns="http://www.w3.org/2000/svg">
    <path
      d="M48 64C21.5 64 0 85.5 0 112c0 15.1 7.1 29.3 19.2 38.4L236.8 313.6c11.4 8.5 27 8.5 38.4 0L492.8 150.4c12.1-9.1 19.2-23.3 19.2-38.4c0-26.5-21.5-48-48-48H48zM0 176V384c0 35.3 28.7 64 64 64H448c35.3 0 64-28.7 64-64V176L294.4 339.2c-22.8 17.1-54 17.1-76.8 0L0 176z"
    ></path>
  </svg>
  <span class="msg-count">99</span>
</button>

<style>
/* From Uiverse.io by vinodjangid07  - Tags: black, notification, button, hover effect, inbox */
.inbox-btn {
  width: 50px;
  height: 50px;
  border-radius: 50%;
  border: none;
  box-shadow: 0px 0px 20px rgba(0, 0, 0, 0.082);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  background-color: #464646;
  cursor: pointer;
  transition: all 0.3s;
}
.inbox-btn svg path {
  fill: white;
}
.inbox-btn svg {
  height: 17px;
  transition: all 0.3s;
}
.msg-count {
  position: absolute;
  top: -5px;
  right: -5px;
  background-color: rgb(255, 255, 255);
  border-radius: 50%;
  font-size: 0.7em;
  color: rgb(0, 0, 0);
  width: 20px;
  height: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.inbox-btn:hover {
  transform: scale(1.1);
}

</style>
    